Union SUM SQL Must have its own alias - sql

Question

I have made some relative posts with the same errors, I have tried almost every solution that has been suggested.
Here is the SQL:
SELECT Sum(h.counter1 + l.counter2) AS hour_amount
FROM (
SELECT 1
FROM xp_hour h
WHERE h.account_id = '1'
AND h.hour_date = Date('2017-03-06')
AND ((
h.from_time < Time('06:00')
AND h.till_time > Time('06:00'))
OR (
h.from_time < Time('15:00')
AND h.till_time > Time('15:00'))
OR (
h.from_time = Time('06:00')
AND h.till_time = Time('15:00'))))
UNION ALL
(
SELECT 1
FROM xp_leave l
WHERE l.account_id = '1'
AND ((
l.from_datetime < Timestamp('2017-03-06 06:00')
AND l.till_datetime > Timestamp('2017-03-06 06:00'))
OR (
l.from_datetime < Timestamp('2017-03-06 15:00')
AND l.till_datetime > Timestamp('2017-03-06 15:00')))) t_union
Error
Error: Every derived table must have its own alias

Answer 1

Try this:
SELECT SUM(h.counter1 + l.counter2) AS hour_amount
FROM (
SELECT 1
FROM xp_hour h
WHERE h.account_id = '1' AND h.hour_date = DATE('2017-03-06') AND
(
(h.from_time < TIME('06:00') AND h.till_time > TIME('06:00')) OR
(h.from_time < TIME('15:00') AND h.till_time > TIME('15:00')) OR
(h.from_time = TIME('06:00') AND h.till_time = TIME('15:00'))
)
UNION ALL
SELECT 1
FROM xp_leave l
WHERE l.account_id = '1' AND
(
(l.from_datetime < TIMESTAMP('2017-03-06 06:00') AND
l.till_datetime > TIMESTAMP('2017-03-06 06:00')) OR
(l.from_datetime < TIMESTAMP('2017-03-06 15:00') AND
l.till_datetime > TIMESTAMP('2017-03-06 15:00'))
)
) t_union
You need to enclose the whole UNION ALL subquery in parentheses, not the individual subqueries that take part in the UNION ALL operation.

Answer 2

Problem is with parenthesis. 1st query is interpreted as separate question which belongs to first from.
Try this:
SELECT SUM(h.counter1 + l.counter2) AS hour_amount FROM
(SELECT 1 FROM xp_hour h WHERE h.account_id = '1' AND h.hour_date = DATE('2017-03-06') AND ((h.from_time < TIME('06:00') AND h.till_time > TIME('06:00')) OR (h.from_time < TIME('15:00') AND h.till_time > TIME('15:00')) OR (h.from_time = TIME('06:00') AND h.till_time = TIME('15:00')))
UNION ALL
(SELECT 1 FROM xp_leave l WHERE l.account_id = '1' AND ((l.from_datetime < TIMESTAMP('2017-03-06 06:00') AND l.till_datetime > TIMESTAMP('2017-03-06 06:00')) OR (l.from_datetime < TIMESTAMP('2017-03-06 15:00') AND l.till_datetime > TIMESTAMP('2017-03-06 15:00'))))) t_union
I remove the last ) from 1st query to end of union

Answer 3

Name a alias for the first part of the derived table before UNION ALL like you put t_union for the 2nd part.
for example:
(SELECT 1
FROM xp_hour h
WHERE h.account_id = '1'
AND h.hour_date = DATE('2017-03-06')
AND ((h.from_time < TIME('06:00')
AND h.till_time > TIME('06:00'))
OR (h.from_time < TIME('15:00')
AND h.till_time > TIME('15:00'))
OR (h.from_time = TIME('06:00')
AND h.till_time = TIME('15:00')))) as t_union_1